1. Field of the Invention
The present invention relates to a surface-coated cermet cutting tool (hereinafter, referred to as a coated cermet tool) of which a hard coating layer exhibits excellent chipping resistance during high-speed intermittent cutting of steel, cast iron, and the like.
2. Description of the Related Art
In recent years, the performance of a cutting tool has been remarkably enhanced, and demands for labor saving and energy saving in cutting work and cost reduction have been increased. Accordingly, the cutting work is more often carried out at a higher speed range. The conventional coated cermet tools generally present no problem when they are used in the continuous cutting or intermittent cutting of steel, cast iron, or the like under normal conditions. Specifically, when the conventional cutting tools are used in a high-speed intermittent cutting under the severest cutting condition, i.e., in the high-speed intermittent cutting in which mechanical impacts are repeatedly applied to the cutting edge at very short pitches, the titanium compound layer which is the lower layer of the hard-coating layer has high-temperature strength and the Al2O3 layer which is the upper layer of the hard coating layer has high-temperature hardness and excellent heat resistance. However, since the high-temperature strength of the titanium compound layer is not sufficient, it is not possible to satisfactorily cope with the mechanical impacts. As a result, chipping (fine cracks) easily occurs in the hard coating layer, consequently shortening the usable life of the coated cermet tools.